A mere two percent of human DNA is involved in manufacturing the body's proteins, and researchers have wondered for decades why the rest of the human genome exists. While the role of this DNA in the body remains largely a mystery, a new study reports that nearly identical versions of this “non-coding” human DNA are present in 14 distantly related mammals. The species include African elephants, mice, pigs, bats, armadillos, and platypuses.

The preservation of this DNA in such distant relatives over the course of evolution suggests that it is important to the health of mammals—otherwise it might have been discarded long ago, the researchers conclude in a report published online today in Science.

In the study Swiss and American researchers identified 191 regions of the genome that are essentially the same among all the species. They started with about 200 regions on human chromosome 21 that are also present in mice and then searched for matches in the other genomes.

Emmanouil Dermitzakis and Stylianos Antonarakis, both of the University of Geneva Medical School, led the project. Other species in the study were green monkey, lemur, porcupine, rabbit, cat, shrew, wallaby, and opossum.

"These conserved regions of the mammalian genomes appear to have characteristics distinct from the elements we already know,” says Dermitzakis. This raises the possibility that the human genome contains functional elements that are totally new to researchers, he adds.

The researchers call the regions “CNGs” for conserved non-genic sequences. More generally, this DNA has sometimes been derided as junk because its role was unknown. But the ability to compare many genomes is allowing researchers to assess the frequency of this DNA among species and whether or not it has been preserved during evolution.